The goal of this research is to develop and clinically implement a new method of quickly and reversibly blocking the conduction of action potentials in peripheral nerve. In our currently funded project, we have demonstrated that high frequency alternating current (HFAC) waveforms produce a block of nerve activity that is completely effective and reversible. Specifically, through in-vivo experimentation and computer modeling we have demonstrated that nerve block can be produced by alternating current waveforms in the 5-30 KHz range when delivered through electrodes encircling the nerve. We have determined that the conduction block occurs locally and has no direct effect on the surrounding nerve or muscle. Although this technique has significant potential application in controlling muscle spasticity and pain, there remain two major impediments to human application. First, the HFAC waveform produces a transient activity in the nerve when it is first turned on. This transient activity can be quite large and last for several seconds. For most human applications it will be necessary to eliminate this activity. Second, it must be demonstrated that the HFAC waveform is safe to both the tissue and electrode when delivered chronically. Therefore we propose to address both of these issues in this project. Modified HFAC waveforms that do not produce the transient activity will be developed through computer simulation and then tested experimentally in-vivo to identify the most promising waveform. We will then develop the necessary technology to produce the modified HFAC waveform for chronic testing in animals. The chronic testing will be performed and analyzed and all other preparations for human application will be completed during this project. At the completion of the proposed project we will be ready to test HFAC nerve block in humans utilizing a percutaneous system. Targeted applications include the relief of muscle spasticity in dystonia, control of muscle spasticity in stroke and relief from neuroma pain after amputation. This research will provide a significant tool in our ongoing efforts to reduce disability and improve quality of life.